Lecture 09 Strings, IDEs.

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Lecture 09Strings, IDEs.
Mon July 29, 2002

• METU Dept. of Computer Eng. Summer 2002
• Ceng230 - Section 01
• Introduction To C Programming
• by Ahmet Sacan

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C String

• is a sequence of one or more characters
  terminated by a NULL ( '\0' )character.
• The NULL character is crucial in determining the
  end of the string.

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Goal Replay..

• Write a function that takes an array as input and
  returns the length of the string.

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• int strlen(char str )
• int i0
• while (stri ! '\0') i
• return i

int strlen(char str) int i0 while (stri
! '\0') i return i
int strlen(char str) char p
str while(p) p return p - str
int strlen(char str) int i0 while
(stri) return i - 1
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ltstring.hgt

• size_t strlen(const char s)
• return length of string ( of chars preceding
  '\0')
• char strcpy (char dest, const char src)
• copies the string src into dest (including
  NULL-char) returns dest.
• char strcat (char dest, const char src)
• concatenates src to the end of dest, adds NULL at
  the end of dest returns dest.
• int strcmp (const char s1, const char s2)
• compares strings s1 and s2, returns a negative
  value if s1 is lexicographically less than s2
  zero if s1 is equal to s2 a positive number if
  s1 is greater than s2.

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• char strchr(const char s, char c)
• returns a pointer to the first occurrence of c in
  the string s. (NULL if not found)
• char strrchr(const char s, char c)
• returns a pointer to the last occurrence of c in
  the string s. (NULL if not found)
• char strstr(const char s1, const char s2)
• returns a pointer to the first occurrence of s2
  in string s1.

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• char strncpy (char dest, const char src,
• size_t n)
• copies at most the first n characters of src into
  dest.
• char strncat (char dest, const char src,
• size_t n)
• concatenates at most n characters of src to the
  end of dest.
• int strncmp (const char s1, const char s2)
• compares at most max(n, s1.length, s2.length)
  characters.

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• size_t an unsigned integral type defined in
  ltstddef.hgt
• const char string parameters that are not
  modified by the function.

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• define MAX 32
• char xMAX, yMAX
• printf("d", strlen("hello.")
• printf("s", strcpy(x, "green"))
• printf("s", strcpy(y, strrchr("blue", 'u') ) )
• x2 '\0'
• printf("s", strcat(x, y) )
• printf("s", strcpy(x, y) )
• printf("d", strcmp(x,y) )
• printf("s", strchr("blackwhite", 'w') )

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Goal

• write your own strcpy(s1, s2) function.
• copies s2 into s1, including NULL-char.
• returns s1

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• char my_strcpy(char dest, char src)
• char todest, fromsrc
• while(to from)
• to, from
• return dest

char my_strcpy(char dest, char src) char
todest, fromsrc while(to from)
return dest
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Goal

• Write your own strcat(s1, s2) function
• appends s2 at the end of s1.

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• char my_strcat (char to, char from)
• strcpy(to strlen(to), from)
• return to

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Goal

• Write strstr(s1,s2) function that locates the
  first occurrence of s2 in s1.

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• char my_strstr(char str, char find)
• char p
• for(p str p strchr(p, find) p)
• if(!strncmp (p, find, strlen(find))
• return p
• return NULL

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String Arrays

• char days732
• "Monday", "Tuesday", "Wednesday",
• "Thursday", "Friday", "Saturday",
• "Sunday"
• printf( "s", days2 )

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• void main()
• char str "flower", p
• int i
• for(p str5 p gt str0 )
• printf("c", p--)
• printf("\n")
• for(p str5, i0 p-i gt str )
• printf("c", (--p - i) )
• printf("\n")
• for(p str5, i0 ilt5 i)
• printf("c", p-i)
• printf("\n")
• for(p str5 p gt str p--)
• printf("c", strp-str )
• printf("\n")

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Goal int-sort cheat.

• Read student grades (integers 0-100) into an
  array, and print in ascending order.

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Goal buble-sort.

• Write a program that reads a list of floats,
  stores them in an array, sorts the numbers in
  ascending order, and prints the ordered list.

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• include ltstdio.hgt
• define MAX_SIZE 1000
• void ReadList(float a , int size)
• void PrintList(float a , int size)
• void BubbleSort(float a , int size)
• void main( )
• int arrMAX_SIZE, size
• ReadList(arr, size)
• PrintList(arr, size)
• BubbleSort(arr, size)
• PrintList(arr, size)

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• void ReadList(float a , int size)
• int i0
• for( iltsize i)
• scanf("f", ai )
• void PrintList(float a , int size)
• int i0
• for( iltsize i)
• printf("f, ", ai)
• printf("\n")

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• void BubbleSort(float a , int size)
• int i, unsorted
• float f
• do
• unsorted 0
• for(i0 iltsize-1 i)
• if(ai gt ai1)
• f ai ai ai1 ai1
  f
• unsorted
• size--
• while(unsorted)

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Goal SelectionSort

• Write a function that sorts an array of floats
  using selection sort algorithm.

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